1. Technical Field
The present invention relates to a method of manufacturing a liquid crystal device.
2. Related Art
Since the past, liquid crystal devices have widely been used as display sections of personal computers, cellular phones, and so on, or light valves or the like of projectors. The liquid crystal device is provided with, for example, a liquid crystal layer held between a pixel electrode and a common electrode, an oriented film for controlling the orientation of the liquid crystal molecules of the liquid crystal layer, and so on. When an electrical field is applied to the liquid crystal layer, the direction angles of the liquid crystal molecules vary, and the polarization state of the light passing through the liquid crystal layer is changed. Thus, a part of the light having passed through the liquid crystal layer is absorbed by a polarization plate to turn out to be the light with a predetermined grayscale, which is then emitted from the liquid crystal device.
Incidentally, as the oriented film described above, there has been known a polymer film made of polyimide processed with a rubbing treatment. By providing the orientation with rubbing treatment, the oriented film can easily be formed. However, there are problems such as difficulty in obtaining uniform orientation or in partially controlling the orientation, display defects easily caused by rubbing mark or generation of dust from rubbing cloth, or degradation of yield by generation of damage in the oriented film due to excessive rubbing treatment. Further, in the equipment, such as a liquid crystal projector, using a high-power light source, an organic substance such as polyimide is decomposed with absorption of the source light or the absorption heat thereof, thereby causing degradation in characteristic of the equipment or reduction of life span of the equipment in some cases.
In order for solving such problems, it is effective to use an oriented film made of an inorganic material (hereinafter referred to as an inorganic oriented film) instead of the oriented film made of an organic material. However, if the inorganic oriented film is used, a moisture-proof property is degraded due to the fact that there exist a lot of polarized hydroxyl groups on the surface thereof or that the film has a porous surface and has low adhesiveness with a seal material. From a viewpoint of improving the moisture-proof property, a hybrid oriented film formed of an inorganic material and an organic material has also been proposed (e.g., JP-A-2007-127757 (referred to as Document 1)).
According to the Document 1, an inorganic oriented film is formed, and then an alkyl group (an organic substance) is coupled on the surface of the inorganic oriented film by executing a surface treatment with a silane-coupling agent on the surface of the inorganic oriented film. Further, two types of silane-coupling agents with molecular weight different from each other are used so that the gap caused by the steric barrier of the alkyl group with greater molecular weight is filled with the alkyl group with smaller molecular weight. Thus, since the surface of the inorganic oriented film is covered by a dense organic film, water repellency thereof is improved, and the adhesiveness with the seal member is also improved.
According to the technology of the Document 1, although the moisture-proof property of the liquid crystal device can dramatically be improved, the characteristics required for the oriented film vary since the liquid crystal devices are used in various devices, and therefore, there are some points to be improved for obtaining the oriented film with desired characteristics.
If the surface treatment with the silane-coupling agent is executed on the inorganic oriented film as described in the Document 1, other characteristics than the water repellency, light resistance and orientation are also varied. Such a characteristic variation depends mainly on the carbon number of the alkyl group coupled to the surface of the inorganic oriented film, and therefore, if the type of the silane-coupling agent is determined, the characteristic of the oriented film is specified. Therefore, in order for obtaining a desired characteristic, it is required to appropriately select the silane-coupling agent, and research and experiments for the selection require a large amount of labor. Further, since the carbon number is a natural number, it is difficult to continuously vary the characteristic of the oriented film, and there is also a disadvantage that the characteristic cannot finely be controlled.